<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    x: {{ x }}
    y: {{ y }}
  </div>
  <script type="module">
    import { createApp, reactive, onMounted, onUnmounted, toRefs } from './node_modules/vue/dist/vue.esm-browser.js'
    function useMousePosition () {
      // 第一个参数 props
      // 第二个参数 context， attrs， emit， slots
      const position = reactive({
        x: 0,
        y: 0
      })
      const update = e => {
        position.x = e.pageX
        position.y = e.pageY
      }
      
      onMounted (() => {
        window.addEventListener('mousemove', update)
      })

      onUnmounted (() => {
        window.removeEventListener('mousemove', update)
      })
      return toRefs(position)
    }
    const app = createApp({
      setup () {
        // const position = useMousePosition()
        const { x, y } = useMousePosition()
        return {
          x,
          y
        }
      }
    })
    console.log(app)
    app.mount('#app')
  </script>
</body>
</html>